In a transmission device, known now for many years, for boat motors, an input shaft drives via a double bevel gearing, an intermediate shaft, which in turn via an additional bevel gear mechanism, drives an output shaft, which can either be the propeller shaft itself or be provided with the flange intended to be coupled to a propeller shaft. The reversing mechanism is integrated into the bevel gear mechanism by it having two freely rotatably mounted bevel gears which can be automatically locked by means of clutch means to the intermediate shaft and which engage a bevel gear on the input shaft.
The clutch means used were inter alia cone clutches, comprising a double clutch cone displaceable on the intermediate shaft between the bevel gears, whereby the clutch cone is displaceable into engagement with a facing conical clutch surface on the respective bevel gear. The displacement of the clutch cone was achieved mechanically and special mechanical devices utilizing the rotation of the shaft were used to overcome the tendancy to self locking which occurs in such clutches and which can create problems with disengagement, especially at high motor torque.
There have recently been developed hydraulically operated multi-disk clutches for locking and releasing the gears in the reversing mechanism. Such an arrangement shown in EP-A-295 569. Two bevel gears on an input shaft are alternately engageable with the shaft to drive an output shaft, which has a bevel gear in engagement with the two gears on the input shaft. The halves of the clutch cooperating with the respective gears are integrated into a unit which is placed between the freely rotatably mounted gears, i.e. near the point of intersection of the rotational axis of the shafts. The use of hydraulically operated clutches instead of mechanically operated cone clutches makes it possible to control engagement smoothly even at very high power, thus eliminating the risk of self locking.
The design of the known multi-disk clutch as a double clutch placed between the releasable gears in the same place as the known cone clutches creates however problems. This is due to the fact that the arrangement requires more space in the axial direction than the cone clutch arrangement, and this means that the gears in the bevel transmission must be made with larger radial dimensions and this makes the entire transmission device with associated housing heavier, more expensive and more space consuming.